Sliding sleeves are widely used in a variety of hydrocarbon production systems. A sliding sleeve typically includes a tubular outer housing having threaded connections at one or both ends for connection to a tubing string. The outer housing also includes one or more flow ports therethrough. Inside the housing, a sleeve mechanism is arranged to slide longitudinally within the outer housing. The sleeve may have one or more flow ports therethrough. The sleeve mechanism can be positioned to align the flow ports in the sleeve with the flow ports in the housing, which will allow fluid flow (either from inside out or outside in). Alternatively, the sleeve mechanism can be positioned so that the flow ports are not aligned, thereby preventing fluid flow. Many variations of this basic concept are known to those skilled in the art, and will not be discussed in detail here. For example, in some embodiments, the sleeve may not have flow ports, but may be arranged to either block the flow ports in the outer housing or not, thereby permitting flow or not.
In many applications, multiple sliding sleeves are used along a tubing string so that a hydrocarbon well can be segmented into a plurality of zones. By opening and/or closing various sliding sleeves, the individual zones can be isolated so that one or more zones can be produced, stimulated, etc. One example of such applications relates to multi-zone fracture systems, which are used, for example, in the Rocky Mountains of the western United States. In such an operation, a series of sliding sleeves are cemented thru as part of the well completion process. A problem with these systems is that cement can get into the inner workings of the sliding sleeves, which can cause problems with operation of the sleeves.
Prior art solutions to this problem have included putting grease into the sleeves to exclude the cement from the inner workings of the sleeve. However, the grease may still be displaced, for example, while the sliding sleeve is being run in or during other operations prior to cementing. Historically, there has been no solution to this problem other than to putting in what was thought to be a sufficient amount of grease and hoping for the best. Therefore, what is needed in the art is a system for preventing the displacement of grease disposed within a sliding sleeve to prevent entry of cement and/or other debris that can interfere with operation of the sliding sleeve.